Studies on the substitution chemistry of tetralin-iron cations and related complexes

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dc.contributor.authorSam, Anthony R.H.en_US
dc.date.accessioned2024-08-15T18:18:48Z
dc.date.available2024-08-15T18:18:48Z
dc.date.copyright1987en_US
dc.date.issued1987
dc.degree.departmentDepartment of Chemistry
dc.degree.levelMaster of Science M.Sc.en
dc.description.abstractThe preparation and spectroscopic properties of substituted tetralin cyclopentadienyliron complexes are described. As a consequence of the activating influence of the cyclopentadienyliron (CpFe+) group, the coordinated tetralin fragment in the arene complex [CpFe+(tetralin)]PF6-exhibits an enhanced susceptibility to attack by nucleophiles and an increased acidity of the benzylic hydrogens. These chemical properties have been utilized to carry out substitution reactions in the aromatic and saturated ring systems of the tetralin ligand. The resulting substitution patterns have been shown, by NMR spectroscopy, to affect the regio- and stereospecificity of electrophilic and nucleophilic additions to the complexed tetralin hydrocarbon. Reactions of the cation [CpFe+(tetralin)] with hydride and carbon nucleophiles afford neutral cyclohexadienyl adducts. In each case, mixtures of two isomers are formed with low to moderate regioselectivity as shown by 1H and 13c NMR spectroscopy. Treatment of the complex [CpFe+(tetralin)]PF6 - with the base Bu t OK results in the deprotonation of the benzylic hydrogens. Subsequent reactions of the deprotonated species with electrophiles (e.g. alkyl halides) afford mono-, tri-, and tetra-substituted tetralin derivatives which are formed with high stereoselectivity in most cases. A preference for exo-substitution by bulky electrophiles in the saturated ring is suggested by 1H NMR spectroscopic data. The addition of hydride and carbon nucleophiles to the coordinated aromatic ring of [CpFe+(tetramethyltetralin)]PF6- proceeds stereo- and regiospecifically due to the steric influence of per-a-methylsubstitution in the saturated ring system. For example, phenyl-lithium addition to the tetramethyltetralin complex yields a single neutral phenyl­cyclohexadienyl adduct. Hydride abstraction of this adduct with Ph3CBF4 affords the cationic monophenyl-tetramethyltetralin derivative. Further treatment of the latter with phenyl-lithium followed by Ph3CBF4 produces the cationic diphenyl-tetramethyltetralin complex. Moderate selectivity is observed in the addition of hydride ion (from LiBEt 3H) to the complex [CpFe+(tribenzyltetralin)]PF6-; however, the analogous reaction involving nucleophilic attack by methyl carbanion (from CH 3Li) proceeds regiospecifically. A preliminary study of the deprotonation chemistry of the heterocyclic arene complex [CpFe+(tetrahydroquinoline)]PF6- is reported. Reactions with Bu t OK and iodomethane afford N-methylated and per-a-methylated derivatives.
dc.format.extent204 pages
dc.identifier.urihttps://hdl.handle.net/1828/19552
dc.rightsAvailable to the World Wide Weben_US
dc.titleStudies on the substitution chemistry of tetralin-iron cations and related complexesen_US
dc.typeThesisen_US

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